1. Field of the Invention
The present invention relates generally to lighting, and more particularly to a ceramic metal halide or arc discharge lamp.
2. Discussion of the Art
Lamp assemblies incorporating a ceramic metal halide arctube are known in the art. For example, a PAR 20 or a PAR 30 lamp refers to a ceramic metal halide arctube received in a capsule mounted in a housing. The light source or arctube is located at the focal point of a parabolic reflective surface to direct light outwardly through a cover or lens at an open end of the housing. The metal halide arctube is a double-ended structure in which first and second legs of the arctube are typically aligned along the longitudinal axis of the housing. The arctube is hermetically sealed within the light transmissive capsule, typically, a quartz material construction. The capsule has electrical connectors or leads that extend outwardly from one end of the capsule for connection with an external power source via, for example, a first contact or threaded shell and a second contact or central eyelet. The external source provides an electrical potential through the parallel outer leads which are connected to a pair of molybdenum foil components sealed (for example, pinch sealed) at the capsule end. The opposite end of the molybdenum foils are electrically connected to arctube leads extending from the legs of the arctube. Thus, due to the elongated double-ended structure of the ceramic metal halide arctube, a frame component or support wire extends from connection with one of the molybdenum foils, and extends in offset, parallel relation to the longitudinal axis of the housing and arctube. It is electrically connected to the arctube lead at the outer end. The capsule is typically tubulated at the outer end that allows the capsule to be exhausted to vacuum levels after pinch sealing the other end of the capsule. The tubulation also helps to center the arctube within the capsule by accommodating a terminal end of the arctube lead inside the tubulation.
Although helpful in aligning or centering the arctube relative to the capsule, and thus relative to the reflector housing, extending the arctube lead into the tubulation for centering purposes increases the overall length of the capsule. That design provides a certain nominal insertion of the arctube lead into the tubulation, plus a nominal spacing between the end of the arctube lead and the tubulation tip-off. Due to these design considerations, use of existing capsules in smaller packages is essentially precluded.
Alternative approaches to arctube centering have been considered with regard to other lamps, but the above described tubulation centering technique has been used exclusively with ceramic metal halide lamps. However, these other approaches suffer from their own problems. For example, a circular wire component or xe2x80x9chaloxe2x80x9d can be welded to a straight wire. The halo serves a centering function of an arctube within a shroud.
Another consideration is to weld first and second thin strips of metal bent into cords whose radii are similar to the inner diameter of the shroud onto the frame component. Again, the necessity for welding the parts to the support lead is undesirable. Likewise, additional material used to center the arctube should be minimized to prevent distortion or shadowing in the beam pattern created by the light source inside the reflector.
Accordingly, a need exists for an effective, economical solution to centering or aligning a ceramic metal halide arc tube within the capsule that overcomes the noted problems and others.
A ceramic metal halide lamp assembly includes an elongated arctube that includes first and second arctube leads extending from first and second ends, respectively. The arctube is hermetically sealed within a light transmissive capsule having first and second electrical connectors extending through a first end thereof An elongated support member or support wire electrically connects the second arctube lead with the second electrical connector and includes a bend region that extends in a circumferential direction dimensioned for abutting receipt within the capsule to provide a centering function of the arctube within the capsule.
An exemplary embodiment includes a bend region comprised of first and second portions spaced from each other.
In an exemplary embodiment, the bend region is located closer to the first end of the capsule than the second end to prevent distortion or shadowing in the beam pattern.